Earplugs are commonly produced by punching a plug out of a plate of material or molding individual earplugs in individual molds. It is also possible to form earplugs by extruding material that is cut into earplugs. U.S. Pat. No. 5,753,015 describes feeding a small diameter core of round cross-section through an extrusion head while resilient foam material is extruded around the core, to provide a continuous extrusion. As the extrusion cools, it is cut into discrete pieces of about 25 mm length to thereby form individual earplugs. Patent publication WO 02/26465 describes extruding foamable material that will form a slow recovery foam, through an extrusion head, and using a knife blade to cut the extrusion whenever it projects by about 25 mm from the extrusion head, to thereby form individual earplugs. In both cases, the individual earplugs resulting from cutting the extrusion as it emerges from the extrusion head, must be packaged. Earplugs which were very easily packaged and withdrawn from the packaging would be of value.
In accordance with one embodiment of the present invention, an earplug arrangement and method for forming it are provided, which enables low cost production, storage, shipping, and dispensing. The earplug arrangement includes multiple earplugs connected in series to form a chain of earplugs. The chain of earplugs is formed by an extrusion of foamable material which is stored in a plurality of loops, with individual earplugs obtained by severing the last earplug in the chain from the rest of the chain. During extrusion, locations of minimum diameter are formed at uniform spacings of about 1 cm to 5 cm to define the opposite ends of earplugs. This facilitates bending of the chain to store it in loops or turns, and facilitates severing of the last earplug from the chain.
In one arrangement, the chain include a core of elastomeric material which is at least twice as stiff as the material of the foam covering that was extruded around the core. The core resist column-like collapse when the earplug is pressed into the ear canal. The core also holds the chain together and allows the ends of the earplugs to be of a small diameter less than one-fourth the maximum diameter along the extrusion, to more clearly define the individual earplugs and facilitate cutting of earplugs from the chain.
The novel features of the invention are set forth with particularity in the appended claims. The invention will be best understood from the following description when read in conjunction with the accompanying drawings.